Index: llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h
===================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -553,6 +553,10 @@
   Instruction *FoldPHIArgLoadIntoPHI(PHINode &PN);
   Instruction *FoldPHIArgZextsIntoPHI(PHINode &PN);
 
+  /// Helper function for FoldPHIArgXIntoPHI() to get debug location for the
+  /// folded operation.
+  DebugLoc PHIArgMergedDebugLoc(PHINode &PN);
+
   Instruction *foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
                            ICmpInst::Predicate Cond, Instruction &I);
   Instruction *foldAllocaCmp(ICmpInst &ICI, const AllocaInst *Alloca,
Index: llvm/trunk/lib/Transforms/InstCombine/InstCombinePHI.cpp
===================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombinePHI.cpp
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombinePHI.cpp
@@ -18,11 +18,27 @@
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/PatternMatch.h"
 #include "llvm/Transforms/Utils/Local.h"
+#include "llvm/IR/DebugInfo.h"
 using namespace llvm;
 using namespace llvm::PatternMatch;
 
 #define DEBUG_TYPE "instcombine"
 
+/// The PHI arguments will be folded into a single operation with a PHI node
+/// as input. The debug location of the single operation will be the merged
+/// locations of the original PHI node arguments.
+DebugLoc InstCombiner::PHIArgMergedDebugLoc(PHINode &PN) {
+  auto *FirstInst = cast<Instruction>(PN.getIncomingValue(0));
+  DILocation *Loc = FirstInst->getDebugLoc();
+
+  for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) {
+    auto *I = cast<Instruction>(PN.getIncomingValue(i));
+    Loc = DILocation::getMergedLocation(Loc, I->getDebugLoc());
+  }
+
+  return Loc;
+}
+
 /// If we have something like phi [add (a,b), add(a,c)] and if a/b/c and the
 /// adds all have a single use, turn this into a phi and a single binop.
 Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
@@ -114,7 +130,7 @@
   for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i)
     NewBinOp->andIRFlags(PN.getIncomingValue(i));
 
-  NewBinOp->setDebugLoc(FirstInst->getDebugLoc());
+  NewBinOp->setDebugLoc(PHIArgMergedDebugLoc(PN));
   return NewBinOp;
 }
 
Index: llvm/trunk/test/DebugInfo/Generic/instcombine-phi.ll
===================================================================
--- llvm/trunk/test/DebugInfo/Generic/instcombine-phi.ll
+++ llvm/trunk/test/DebugInfo/Generic/instcombine-phi.ll
@@ -0,0 +1,70 @@
+; RUN: opt -instcombine -S < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; If all the operands to a phi node are of the same operation, instcombine
+; will try to pull them through the phi node, combining them into a single
+; operation.  Check that when it does this the combined operation does not
+; have a debug location set.
+
+; Test folding of a binary operation.  Generated from source:
+
+; extern int foo(void);
+; extern int bar(void);
+; 
+; int binop(int a, int b) {
+;   if(a)
+;     b -= foo();
+;   else
+;     b -= bar();
+;   return b;
+; }
+
+; CHECK: define i32 @binop
+; CHECK-LABEL: if.end:
+; CHECK: %[[PHI:.*]] = phi i32 [ %call, %if.then ], [ %call1, %if.else ]
+; CHECK: sub nsw i32 %b, %[[PHI]]
+; CHECK-NOT: !dbg
+; CHECK: ret i32
+
+define i32 @binop(i32 %a, i32 %b) !dbg !6 {
+entry:
+  %tobool = icmp ne i32 %a, 0, !dbg !8
+  br i1 %tobool, label %if.then, label %if.else, !dbg !8
+
+if.then:                                          ; preds = %entry
+  %call = call i32 @foo(), !dbg !9
+  %sub = sub nsw i32 %b, %call, !dbg !10
+  br label %if.end, !dbg !11
+
+if.else:                                          ; preds = %entry
+  %call1 = call i32 @bar(), !dbg !12
+  %sub2 = sub nsw i32 %b, %call1, !dbg !13
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  %b.addr.0 = phi i32 [ %sub, %if.then ], [ %sub2, %if.else ]
+  ret i32 %b.addr.0, !dbg !14
+}
+
+declare i32 @foo()
+declare i32 @bar()
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "", isOptimized: false, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2)
+!1 = !DIFile(filename: "test.c", directory: "")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!6 = distinct !DISubprogram(name: "binop", scope: !1, file: !1, line: 8, type: !7, isLocal: false, isDefinition: true, scopeLine: 8, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!7 = !DISubroutineType(types: !2)
+!8 = !DILocation(line: 9, column: 6, scope: !6)
+!9 = !DILocation(line: 10, column: 10, scope: !6)
+!10 = !DILocation(line: 10, column: 7, scope: !6)
+!11 = !DILocation(line: 10, column: 5, scope: !6)
+!12 = !DILocation(line: 12, column: 10, scope: !6)
+!13 = !DILocation(line: 12, column: 7, scope: !6)
+!14 = !DILocation(line: 13, column: 3, scope: !6)